JP7252307B2 - Compositions and methods for making water-soluble penetrating inkjet inks - Google Patents

Description

1. TECHNICAL FIELD OF THE INVENTION This invention relates to compositions and methods of making security inks for use in inkjet printers.

2. Description of the Related Art As printing technology has become more sophisticated and printers have become more readily available to the public, more and more documents are being printed on demand. The inherent value of some of these documents, such as personal checks, shares, banknotes, wills, deeds and drug prescriptions, has attracted counterfeiters to alter or reproduce them.

Most printing systems print by placing ink or toner on the surface of the substrate on which the ink or toner rests and the image is formed. Some inks and toners can be removed from the surface of the substrate relatively easily by rubbing them or using solvents. These documents are easy targets for forgery.

Systems have been developed over the years to prevent this type of document tampering. For example, Snyder, US Pat. No. 1,727,912, discloses a form of paper that can be used to protect the integrity of information printed on the paper. The paper includes a coating with relatively low ink absorption properties and a body that readily absorbs ink. A secure document is created by cutting or tearing the coating during the writing process so that the ink penetrates into the paper's absorber. Once the ink is absorbed, it is difficult to remove. This specialized paper is expensive due to the materials and manufacturing methods required for its manufacture.

Gruber et al. US Pat. No. 5,124,217, discloses a secure printing toner for electrophotographic printing. The toner produces a color smear indicative of an attempted counterfeiting when exposed to a common solvent often used in document counterfeiting, namely toluene.

Heilman et al. US Pat. No. 7,220,524, discloses color penetrating toners that can be used in laser printers. The toner is typically used with substrates that have special coatings to aid penetration. After penetration, it is difficult to remove the toner printed image.

There is a need for relatively inexpensive penetrating inks that can be used in inkjet printers that provide desirable penetrating properties to provide additional security features to documents.

A water-soluble penetrating ink with two colorants, a pigment and a water-soluble dye, a humectant in which the water-soluble dye is at least partially soluble, and water provides a security ink that can be used in an inkjet printer.

The amount of wetting agent used is between 20% and 70% by weight. The wetting agent selected provides relatively slow evaporation of the solvent mixture of wetting agent and water. Pigments do not dissolve in wetting agents or water. Most of the pigment will not penetrate the substrate and will form an image on the printing surface of the substrate. A slow evaporation rate of the solvent mixture allows the solvent mixture to carry the dyes to the substrate. After this transfer, the dye forms an image on the non-printing side of the substrate.

A pigment dispersion with the desired particle size is the first step in the process of making an ink. Dyes, wetting agents, water and pigment dispersions are mixed. Those ingredients may be added one by one. The result is the security ink according to the present invention.

The precise nature of this invention, as well as its objectives and advantages thereof, will become readily apparent from a consideration of the following specification, taken in conjunction with the accompanying drawings, in which like numerals denote like parts throughout the figures. It will be.
1 is a block diagram illustrating a preferred method for making water soluble penetrating inkjet inks; FIG. 2 is a photograph of the surface of a substrate printed with the water-soluble penetrating inkjet ink of FIG. 1; 3 is a photograph of the non-printing side of the substrate of FIG. 2 showing the penetration of the water-soluble penetrating inkjet ink;

The inventors have discovered a method of making relatively inexpensive inks for ink jet printers that provide desirable penetration properties. The ink is water-based and a coating is not required for dye transfer. The dye migrates through the substrate immediately after printing.

Inkjet inks contain two types of colorants: pigments and water-soluble dyes. The pigment color and dye color may be the same or different. The ink also contains a slow-drying humectant in which the dye dissolves. When printed onto a porous substrate such as paper, the pigments form an image on the printing surface of the substrate. Pigments do not dissolve in wetting agents and therefore remain on the surface of the substrate. Wetting agents carry dissolved dyes through the substrate. Ultimately, the humectant and dye penetrate sufficiently into the substrate that the dye forms an image on the opposite, non-printing side.

The security features of penetrating inks can be increased by using UV responsive dyes. After penetration, UV dyes may appear colorless or colored on the non-printing side of the substrate. However, when UV light is used to illuminate the non-printed surface, the dye fluoresces. The authenticity of the document can be verified by comparing the fluorescent image with the pigment-based image.

Inkjet inks may also include one or more of penetrants or surfactants, and may include biocides, fungicides, bactericides, anti-curl agents, anti-bleed agents, anti-kogation agents, surface tension modifiers, or any other known additives such as buffers.

Preferred dyes used in inks exhibit strong color absorption through the substrate, good solubility in the selected humectant(s), and good stability in the final ink, and are indelible. The dye may or may not be UV responsive. By way of example, suitable UV responsive dyes include Acid Red 52, Basic Red 14, Basic Red 15, Acid Yellow 73, Direct Yellow 96, Basic Yellow 40, and Direct Yellow 73. As further examples, suitable non-fluorescent dyes include Acid Red 1, Acid Red 14, Acid Red 88, Basic Red 18, Basic Violet 1, Basic Violet 3, Direct Red 31, Direct Red 23, Reactive Red 2, Reactive Includes Red 11, most acid yellow and acid blue dyes, most direct yellow and direct blue dyes, most basic yellow and basic blue dyes, and most reactive yellow and reactive blue dyes.

The pigment may be a pigment dispersion. Pigment dispersions are well known in the art and will not be described here. It is desirable for the pigment particles in the pigment dispersion to be small enough to flow freely through the nozzles of an ink jet printer. A typical inkjet printer nozzle has a diameter of 10 micrometers (10 microns) to 50 microns, and most nozzles have a diameter of less than 30 microns. The particle size of the pigment is preferably also selected to maintain the stability of the pigment in the ink. Therefore, smaller particles are preferred over larger particles. By way of example, suitable pigment sizes are from 200 nanometers (nm) to 20 microns in size, and preferably from 100 nm to 20 microns in size.

Typical pigments include azo pigments such as condensed azo pigments and chelated azo pigments; polycyclic pigments such as phthalocyanines, anthraquinones, quinacridones, thioindigoids, isoindolinones and quinophthalones; nitro pigments; and daylight fluorescent pigments; titanium oxide; zinc oxide; magnetic iron oxide and carbon black; carbon black, organic and inorganic colored pigments, magnetic iron oxide, composite black. Preferred pigments include carbon black, magnetic iron oxides, and pigments capable of producing cyan, magenta, and yellow inks. By way of example, suitable pigments are carbon black, magnetic iron oxide, Pigment Red 81, Pigment Red 122, Pigment Yellow 13, Pigment Yellow 14, Pigment Yellow 17, Pigment Yellow 74, Pigment Yellow 83, Pigment Yellow 128, Pigment Yellow 138. , Pigment Orange 5, Pigment Orange 30, Pigment Orange 34, Pigment Blue 15:4, and Pigment Blue 15:3.

Wetting agents carry dyes. They move together through the porous substrate. The ink may include multiple humectants and includes water. Wetting agents should be selected so that the dye is at least partially soluble in each. Any humectant can be used as long as the dye is sufficiently soluble in the solvent mixture containing the humectant and water.

The humectant should have a sufficiently slow evaporation rate so that the humectant travels through the thickness of the substrate before drying. However, if the wetting agent evaporates too slowly, it will not stop moving after reaching the non-printing side of the substrate. This excessive migration can result in a hazy image and dye bleeding from the substrate. The evaporation rate of the humectant must be slow enough to allow penetration through the substrate and fast enough to prevent excessive migration.

Evaporation rates of materials are typically not measured. However, the boiling point of the material is well known and corresponds to the evaporation rate. In particular, higher boiling points typically correspond to slower rates of evaporation. Water, for example, has a boiling point of one hundred degrees Celsius (100°C) and ethylene glycol has a boiling point of 197°C. Based on boiling point, it is known that water evaporates faster than ethylene glycol.

The type and amount of wetting agent should be selected to reach the desired boiling point of the solvent mixture (wetting agent and water combination). In particular, the boiling point of the solvent mixture should be high enough to allow penetration of the dye through the substrate and high enough to minimize any haze or bleed caused by excessive migration of the dye. should be low.

The boiling point of the solvent mixture should be above 100° C. (the boiling point of water). By way of example, suitable boiling points for solvent mixtures are 100°C to 400°C, 150°C to 400°C, 175°C to 400°C, or 200°C to 400°C.

To achieve the desired solubility and evaporation properties, the total amount of non-aqueous humectant in the penetrating inkjet ink is 20% to 70% by weight, 30% to 65% by weight, or 45% to 70% by weight. should be.

Table 1 below shows the boiling point and solubility of the dyes in three typical wetting agents. Solubility was tested by dissolving 1.5 grams (1.5 g) of dye in 6 g of each corresponding solvent.

Each of the wetting agents has a higher boiling point than water. Based on the boiling point and solubility of Acid Red 52, suitable wetting agents are: 2-pyrrolidone; Dowanol™ PM glycol ether; di(ethylene glycol) ethyl ether; ethylene glycol; Contains hexyl carbitol. 1,3-propanediol; 1,5-pentanediol; Dowanol™ PPH glycol ether; triethylene glycol, provided Acid Red 52 is soluble in the final solvent mixture of wetting agent and water glycerol; and 1-(2-hydroxyethyl)-2-pyrrolidone can be used with Acid Red 52.

The use of penetrants is preferred, but optional. It is typically preferred to include one or more penetrants, as penetrants aid in dye transfer. Typical penetrants include 1,2-C1-C6 alkyldiols such as 1,2-hexanediol, N-propanol, isopropanol, and hexylcarbitol. By way of example, the penetrant is present at 0.1% to 10% by weight.

Surfactants are preferred. Surfactants adjust the surface tension and/or viscosity of the penetrating ink. Surfactants are used to control the jetting and wetting properties of the ink and to help the ink penetrate through the substrate. The ink should contain only the minimum amount of surfactant necessary to achieve reliable jetting, wetting, and penetration, especially when pigment dispersions are used. A polymeric dispersant is positioned on the surface of the pigment particles. Surfactants typically have a low molecular weight and may attack polymeric dispersants. When the surfactant is used above the minimum amount, the surfactant will lead to dispersion instability. To achieve the desired jettability, the amount of total surfactant in the penetrating ink is 0 wt% to 2 wt%, 0.01 wt% to 2 wt%, or 0.1 wt% to 2 wt%. should be %.

Nonionic surfactants are preferred. Typical surfactants are Capstone® surfactants available from DuPont of Wilmington, DE; Advanced Polymer, Inc. of Carlstadt, NJ; APFS® surfactants available from Chemguard Inc. of Mansfield, TX. Chemguard®, St. Fluorosurfactants such as Nevec available from 3M of Paul, MN; alkylaryls such as octylphenoxypolyethoxyethanol available from The Dow Chemical Company of Midland, Ml under the trade name TRITON®; Polyether alcohol nonionic surfactants; available from The Dow Chemical Company of Midland, MI under the trade name TRITON®, including TRITON® CF-10, and the trade name TERGITOL®. , alkylamine ethoxylate nonionic surfactants; under the tradenames SURFYNOL® and Dynol® from Air Products and Chemicals, Inc. of Allentown, PA. ethoxylated acetylenediol surfactants available from ICI Chemicals & Polymers Ltd. of Middlesborough, UK under the trade name TWEEN®; Polyalkylene and polyalkylene-modified surfactants available from Crompton OSI Specialties, Greenwich, Conn., under the trade name SILWET®; under the trade name COATOSIL®. by Momentive Performance Materials Inc. of Waterford, NY. polydimethylsiloxane copolymers and surfactants, available from Uniqema, New Castle, DE under the trade names RENEX®, BRIJ® and UKANIL®, available from Uniqema, Inc.; alcohol alkoxylate nonionic surfactants; sorbitan ester products available from Omya Peralta GmbH of Hamburg, Germany under the trade names SPAN® and ARLACEL®; trade name TWEEN® , ATLAS®, MYRJ® and CIRRASOL® from ICI Chemicals & Polymers Ltd. of Middlesborough, UK. alkoxylated ester/polyethylene glycol surfactants available from Chemron Corporation of Paso Robles, CA under the trade name CHEMPHOS® TR 421;
Alkyl Phosphate Ester Surfactant Products, such as Amyl Acid Phosphate, available from Alkyl Amine Oxide, available from Chemron Corporation of Paso Robles, CA under the trade name CHEMOXIDE®; anionic sarcosinate surfactants available from Hampshire Chemical Corporation of Nashua, NH under the trade name HAMPOSYL®; from Henkei-Nopco A/S, Drammen, Norway under the trade name ALPHENATE®; from Hoechst AG, Frankfurt, Germany under the trade name SOLEGAL® W; ) from Auschem SpA, Milan, Italy under the trade name NEWKALGEN® available from Takemoto Oil and Fact Co., Japan under the trade name NEWKALGEN®. Ltd. modified poly-dimethyl-silicone surfactants available from BYK Chemie of Wesel, Germany under the trade name BYK® 300; and other commercially available surfactants known to those of skill in the art.

Penetrating inks may also contain other additives known in the art. These additives may be chelating agents, buffers, biocides, fungicides, bactericides, anti-curl agents, anti-bleed agents, anti-kogation agents, surface tension modifiers, or buffers. Acceptable biocides include benz-isothiazolin-one, methyl-isothiazolin-one, chloro-methyl-isothiazolin-one, sodium dihydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, Contains sodium benzoate and sodium pentachlorophenol. By way of example, biocides are available from The Dow Chemical Co. of Midland, MI. Proxel™ available from Lonza of Basel, Switzerland; The Dow Chemical Co. of Midland, MI; available from The Dow Chemical Co. of Midland, MI; Givguard(TM), available from The Dow Chemical Co. of Midland, MI; Kathon® PFM, available from Epson;

Turning to FIG. 1, a method (100) of preparing a water-soluble penetrating inkjet ink is shown. The method begins with preparing a pigment dispersion in step (102). Pigment dispersions typically include pigment particles, a dispersant, a solvent, and water. The ingredients were premixed and then transferred to the grinder. The mixture is milled until the desired particle size is achieved.

In step (104), the pigment or pigment dispersion, dye, wetting agent, penetrant, surfactant, water, and any additional additives are mixed together. Ingredients may be added one at a time or may be mixed in time before another ingredient is added. The time between adding ingredients may be 3-20 minutes, or 5-15 minutes. A typical mixing step begins with mixing pigment and water. After about 10 minutes, the humectant is mixed with water, pigment, and the like.

After all ingredients are mixed, the pH of the solution is adjusted to a value between 6.5 and 9.

Table 2 below illustrates nine water-soluble penetrating inkjet ink compositions according to the present invention. Values given are weight percentages of ingredients in the final water-soluble penetrating inkjet ink.

Wetting agent 1 in the examples is 2-pyrrolidinone. However, any wetting agent that has a boiling point above 200° C. and in which the dye is at least partially soluble can be used in place of 2-pyrrolidinone to achieve similar results.

Humectant 2 in the examples is Dowanol™ PM glycol ether. However, any humectant in which the dye has high solubility may be used in place of the Dowanol™ PM glycol ether to achieve similar results. High solubility corresponds to the soluble dyes in Table 1.

Wetting agent 3 in the examples is 1-methoxyl-2-propanol. A humectant 3 is used to adjust the jetting properties of the ink. Any other humectant may be used in place of 1-methoxyl-2-propanol such as glycols, diols or triols to achieve the desired jettability.

An example penetrant is 1,2-hexanediol. Any other penetrant may be used in place of 1,2-hexanediol such as 1,2-C1-C6 alkyl diols.

The water-soluble penetrating inkjet inks described above are commercially available from Hewlett-Packard, Inc. of Palo Alto, CA. was evaluated on the HP Officejet 100 mobile printer, available from HP. The ink was printed on non-fluorescent (UV dull) paper. Table 3 below shows the results printed with each of the penetrating inks of Table 2.

The intensity of the red or yellow color and the fluorescence of the dye on the non-printed side of the paper were rated visually from 1 (weak) to 5 (strong). The results show that increasing the amount of Wetting Agent 2 (in which the dye is highly soluble) increased the color intensity and strength of the fluorescence on the non-printing side of the paper. The results also show that by using surfactants with high wetting properties,
It shows that the color intensity and strength of the fluorescence on the non-printed side of the paper increased.

2 and 3, front and back views of a document printed using the ink composition of Example 8 are shown. In particular, FIG. 2 shows a printed side 200 of a document. FIG. 3 shows the non-printing side 300 of the document illuminated with UV light to cause the dye to fluoresce. The color of the pigment 202 on the printing surface 200 is dark and the characters are clear. On the non-printed side 300, when illuminated by UV light, the Acid Red 52 dye is darker and the letters are clearer.

Claims (15)

A water- soluble ink for use in an inkjet printer , comprising:
a solvent mixture of water and one or more humectants, wherein the humectants are present in the water-soluble ink at 30% to 70% by weight, and the solvent mixture has a boiling point of 100°C to 400°C; a solvent mixture;
a pigment dispersed in the solvent mixture ;
a water-soluble dye that is soluble in the solvent mixture ;
wherein after the water-soluble ink is printed on a substrate by an inkjet printer, the pigment forms an image that is visible from the printing surface of the substrate, and the water-soluble dye is non-printable on the substrate. A water- soluble ink used to form an image opposite to that formed by said pigment that is visible from the side . 2. The water-soluble ink of claim 1, wherein said humectant comprises two humectants, each humectant having a boiling point above 200[deg.]C, and a water-soluble dye soluble in said humectant. The humectant is 2-pyrrolidone, propylene glycol methyl ether, di(ethylene glycol) ethyl ether, ethylene glycol, hexylcarbitol, 1,3-propanediol, 1,5-pentanediol, propylene glycol phenyl ether, triethylene. 3. The water-soluble ink according to claim 1, comprising at least two selected from the group consisting of glycol, glycerol and 1-(2-hydroxyethyl)-2-pyrrolidone. The water-soluble ink according to any one of claims 1 to 3, wherein the solvent mixture has a boiling point of 150°C to 400°C. further comprising a penetrant present at 0.1% to 10% by weight in the water-soluble ink, said penetrant being at least selected from the group consisting of 1,2-C1-C6 alkyldiols, N-propanol and isopropanol; The water-soluble ink of any one of claims 1-4, comprising one. The water-soluble ink of any one of claims 1-5, further comprising a surfactant present at 0.1% to 2% by weight in the water-soluble ink. The water-soluble ink according to any one of claims 1 to 6, wherein the water-soluble dye contains at least one selected from the group consisting of UV-responsive dyes and non-fluorescent dyes. A water-soluble ink according to any preceding claim, wherein the humectant is present in the water-soluble ink at 45% to 70% by weight. A water-soluble ink according to any one of claims 1 to 8, wherein said pigment has a particle size of 200 nm to 20 µm. The water-soluble ink according to any one of claims 1 to 9, wherein the pigment contains at least one selected from the group consisting of carbon black, magnetic iron oxide, organic coloring pigments and inorganic coloring pigments. The water-soluble dyes are Acid Red 52, Basic Red 14, Basic Red 15, Acid Yellow 73, Direct Yellow 96, Basic Yellow 40, Direct Yellow 73, Acid Red 1, Acid Red 14, Acid Red 88, Basic Red 18, 11. The method according to any one of claims 1 to 10, comprising at least one selected from the group consisting of Basic Violet 1, Basic Violet 3, Direct Red 31, Direct Red 23, Reactive Red 2 and Reactive Red 11. water-soluble ink. The pigments include carbon black, magnetic iron oxide, composite black, azo pigments, polycyclic pigments, nitro pigments, daylight fluorescent pigments, carbonates, chromates, titanium oxide, zinc oxide, Pigment Red 81 and Pigment Red 122. , Pigment Yellow 13, Pigment Yellow 14, Pigment Yellow 17, Pigment Yellow 74, Pigment Yellow 83, Pigment Yellow 128, Pigment Yellow 138, Pigment Orange 5, Pigment Orange 30, Pigment Orange 34, Pigment Blue 15:4 and Pigment Blue 15 12. The water-soluble ink according to any one of claims 1 to 11, comprising at least one selected from the group consisting of: 3; A method for producing the water-soluble ink according to any one of claims 1 to 12,
preparing a pigment dispersion;
mixing a water-soluble dye that is soluble in a solvent mixture of water and one or more humectants, said humectants, and water into said pigment dispersion, wherein said humectants are from 30% by weight in the mixture to present at 70% by weight and the boiling point of said solvent mixture is between 100°C and 400°C;
A manufacturing method, including: 14. The method of making a water-soluble ink according to claim 13, wherein the humectant comprises a first humectant having a boiling point above 200<0>C. 15. A method of making a water-soluble ink according to claim 13 or 14, wherein the amount and type of said humectant are selected such that the boiling point of said solvent mixture is higher than 175[deg.]C.

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